Studies show varying flu vaccine effectiveness in Europe
Analysis of six European studies on the 2019/2020 influenza season indicate the interim vaccine effectiveness (VE) against laboratory-confirmed influenza in the primary care setting ranged from 29% to 61% and from 35% to 60% in hospitalized older adults. The results appeared today in Eurosurveillance.
The studies, conducted in 10 countries (Denmark, Spain, Portugal, France, Germany, Romania, Sweden, the Netherlands, Ireland, and the UK) involved a total of 31,537 patients, of which 5,300 were cases (17%) with 5,310 infections. Overall, 84% of confirmed infections were influenza A-positive and 16% were influenza-B positive. Against all subtypes of influenza A among all ages, point estimates for VE ranged from 30% to 60% in primary care and hospitals, and were slightly higher (49% to 62%) in target vaccination groups. Against 2009 H1N1, VE ranged from 48% to 75%. In most studies, the 2019/2020 interim VE against 2009 H1N1 was higher than the 2018/2019 estimates.
Results for VE against H3N2 in the six studies varied widely, ranging from -58% to 57% in primary care and -16% to 60% in hospitals. Against laboratory-confirmed influenza B, VE among all ages ranged from 62% to 83% in primary care settings. The vast majority of circulating influenza B belonged to the B/Victoria lineage, which was the lineage included in the trivalent vaccine but of another subgroup.
For adults over 65, the six studies had VE point estimates of 43% to 66% across all settings.
The authors of the study say VE and antigenic studies at the end of the 2019/2020 season will help explain the age-, subtype-, and study-specific differences seen in the interim results.
Mar 12 Eurosurveill study
Study: 3-drug antimalarial regimens effective, could delay resistance
Adding a third drug to the typical two-drug antimalarial regimen might be an effective strategy in regions where drug resistance is widespread, according to study published yesterday in The Lancet.
Led by researchers at Mahidol University in Bangkok, the multicenter, open-label, randomized clinical trial found that triple artemisinin-based combination therapies (TACTs) could effectively treat malaria caused by Plasmodium falciparum and delay the development of antimalarial drug resistance.
The investigators randomly assigned 1,110 patients at 18 hospitals and clinics in eight countries to either a two-drug or three-drug combination, depending on their location, from Aug 7, 2015, to Feb 8, 2018. Median age was 23 years, and 78% of patients were male. The patients were followed weekly for 42 days, when their response to the drugs was determined via polymerase chain reaction.
The researchers found that the combinations of dihydroartemisinin–piperaquine plus mefloquine and artemether–lumefantrine plus amodiaquine, both of which are TACTs, were effective, safe, and well-tolerated.
Typical antimalarial regimens combine the drug artemisinin, which quickly kills the parasites, with a slower-acting drug such as mefloquine or piperaquine to eliminate any remaining parasites and oppose resistance to artemisinin. Resistance to artemisinin is common in parts of Southeast Asia, where malaria is widespread, which delays elimination of the parasites. Also, the emergence of resistance to mefloquine and piperaquine has become a pressing concern.
The study found that, in areas with widespread resistance to artemisinin, 42-day responses were 98% (95% confidence interval [CI], 94 to 100) with dihydroartemisinin–piperaquine plus mefloquine, compared with 48% (95% CI, 39 to 56) with dihydroartemisinin–piperaquine.
In a commentary in the same issue, Philip Rosenthal, MD, of the University of California at San Francisco, said the results suggest that TACTs might replace ACTs for a time in some areas. "This study offers promise for TACTs in regions with artemisinin resistance, but whether we should implement TACTs in other areas is uncertain," he said. "In any event, TACTs should be seen as a stopgap; novel combination therapies to treat malaria are greatly needed."
Mar 11 Lancet study
Mar 11 Lancet commentary